Alright, well the things I listed originally are your best bets for big gains on a charisma check. I also just remembered that being an Illumian (human-ish race from Races of Destiny) lets you get +2 on charisma checks as a racial feature. But it gives no racial charisma bonus, so compared to a +2 charisma race, it's only a net +1 better for the checks. Every little bit, though...